class_docstr: Test upgrade_opt behavior.
code: def test_eval_vocab(self):
      args = self._get_args()
      args["eval_candidates"] = "vocab"
      args["encode_candidate_vecs"] = True
      valid, test = testing_utils.train_model(args)
  
      # accuracy should be zero, none of the vocab candidates should be the
      # correct label
      self.assertEqual(valid["hits@100"], 0)
  
imports: import os
  import pytest
  import unittest
  import parlai.utils.testing
  from parlai.tasks.integration_tests.agents import CandidateTeacher
label_desc: Use image node_id 10 for calling the _AbstractTRATest obj's underlying member method code with example usage: obj.test_eval_vocab() without return types